1. Field
An aspect of the disclosed technology relates to a touch screen panel, and more particularly, to a flexible touch screen panel and a fabrication method thereof.
2. Description of the Related Technology
A touch screen panel is an input device that through (often, capacitive) contact sensing allows a user's instruction to be manually input by selecting a portion of display that contains a visual cue or instruction content such as an icon.
To this end, the touch screen panel is formed on a display face of an image display device to convert a contact position into an electrical signal. Here, the user's finger(s) or object, such as a stylus, is placed directly in contact with the panel at the contact position. Accordingly, the selection of instruction content at the contact position is received as an input signal to the display.
Since such a touch screen can be substituted for a separate input device, such as a keyboard or mouse, connected to the machine that includes the display, e.g., a mobile tablet or smartphone, its fields of application have been expanding.
In general, touch screen panels employ technologies that can be categorized into resistive overlay, photosensitive, capacitive, and the like. Among these technologies, the capacitive type converts a contact position into an electrical signal by sensing a change in capacitance formed between a conductive sensing electrode and an adjacent sensing electrode or ground electrode when contact is made with a portion of the touch screen panel.
Generally, such a touch screen panel is frequently commercialized by being attached to the display side of a flat panel display device such as a liquid crystal display (LCD) or organic light emitting diode (OLED) display. Therefore, when used as an overlay, a touch screen panel requires characteristics of high transparency and minimal thickness.
Flexible image display device have been developed and commercialized, and naturally, an attached touch screen panel also requires flexibility. In general, the sensing electrodes are implemented using a transparent conductive material. However, when the flexible touch screen panel is bent or folded, cracks occur in the sensing electrodes, and therefore, open circuits cause no capacitive signals to be generated along the lines of broken electrodes causing the entire display to no longer be of use.
In touch screen manufacturing, subprocesses including a thin-film growth process, a pattern formation process, and the like are necessary for forming the sensing electrodes and the like, and therefore, characteristics such as high thermal resistance and chemical resistance are required. Accordingly, the sensing electrodes and related electrical lines are formed on a glass substrate according to the resultant process characteristics. However, in the manufacturing of a rigid display, the glass substrate should have a certain amount of thickness so as to be carried during processes. Therefore, the glass substrate does not satisfy characteristics requiring the reduced thickness and will not be flexible.